Liquid fuel for metallurgical furnaces



Patented Aug. 2, 1932 sra'rss FRANZ PUENING, OF PITTSBURGH, PENNSYLVANIA FFICE LIQUID FUEL FOR METALLURGICAL FURNACES No Drawing.

is approximately 250 million gallons per year. its value as a fuel for heating is around 3 cents per gallon, yet it is known that about of this taris creosote oil which is a wood preservative and which at present has a price of 12 cents per gallon. The demand for creosote oil is so great in this country that a large quantity of it, probably in excess of million gallons per year, is imported into this country,

It has therefore for .many years been thought desirable and often proposed to the owners of open hearth furnaces burning high temperature coke oven'tar, that the valuable creosote oil present in their tar should be removed and only the residue burned. However, a number of serious difiiculties stand in the way of this suggestion. For instance; if all creosote oil present in the'high temperature coke oven tar were removed from it the remaining pitch would be solid' and brittle at ordinary temperature and would have to be preheated to about 500 F. in order to become liquid enough to be sprayed into the open hearth furnace. This high temperature is very objectionable since it is diflicult to maintain it in long lines scattered'over a big open heart plant, and it is also dangerous because a break in the lines would fill the whole place with viscous pitch fumes and most likely cause a fire.

Even if one were satisfied to remove only a portion of the creosote oil from the high temperature coke oven tar, for instance one half of the amount present in it, the remaining pitch, while softer, would still have to be preheated to a temperature of about 250 F., to become sufficiently fluid for spraying. Steam lines would have to be laid parallel to the pitch lines and insulated together with them, thus causing a great expense. Damage from a break of the lines while reduced, would still be probable; and solidification of the If one of these burners receives a lump of vis- Application filed August 5, 1925. Serial No. 48,380.

pitch in the pitch lines and freezing and breaking of the parallel steam lines would be an occurrence, especially frequent in winter. The removal of all or even a portion of the creosote oil is objectionable to the owner of open hearth furnaces also because the total volume of fuel available for his furnaces is thus reduced.

I have therefore thought. of overcoming these difficulties by substitution of other oils into the high temperature coke oven tar after the creosote oil has been removed. I have, however, found that by far the most of the available crude or fuel oils do not dissolve the pitch so thoroughly that a new homogeneous body is created. To the contrary, even though they have been mixed forcibly and may seem to have dissolved each other, they separate again, the pitch isolating itself again, forming a stringy heterogeneous mass, often also precipitating carbon. The fuel is therefore uneven, certain portions being thin fluid, while others are rather viscous. The flow of this liquid through pipes, valves and atomizing burners is therefore by necessity irregular, resulting in an unsteady unsatisfactory flame. This is especially troublesome when several burners are connected to the same line, supplied by the same pump.

cons pitch and thus becomes blocked, the other burners receive the excess of the liquid and develop too much heat. This is an intolerable situation for the operation of any plant.

A certain type of petroleum oils from alimited number of wells seems to be somewhat more disposed, to dissolve high temperature coke oven tar pitch, than the great bulk of the oils. However, it would yet be a precarious undertaking to base the operation of the open hearth plant upon the supply of these oils. It is to be expected that after having selected a particular oil from certain oil wells, and after having adjusted conditions of mixing, preheating, and regulating valves and after having trained the operating crew to handle the new fuel the oil wells occasionally will give out, or the price of the oil may become too high, due to shortage of oil.

That this shortage is coming sooner or later is rather certain. As a result of all these difficulties, owners of open hearth furnaces refuse to part with even a portion of their very convenient tar fuel.

Considering these objections, the idea came to me that low temperature tar, mainly the one distilled from coal, might be an ideal material for dissolving the pitch, remaining after removing the creosote oil from high temperature coke oven tar. It is a mixture of numegg ushydrocarbons, many yet unnew? but preponderantly of cyclic structure, giving upon distillation a steadily rising boiling curve. The acidic portions in it, while of too low a gravity to be attractive to the creosoter, are an excellent substance for dissolving the high temperature coke oven tar pitch, and indeed, upon testing, I found that it mixes easily with hot pitch and completely .dissolves and absorbs it and keeps it in solution, not precipitating free carbon. The solution is permanent; no nests of harder and softer material are formed afterwards by separation. Perfect flow in'pipes is the result and a very moderate preheat is suflicient to giveit the required fluidity for perfect'atomization; a steady smokeless flame'is thusproduced. Y

Fundamentally, therefore, my invention involves the important discovery that coke oven or high temperature tar-pitch is easily miscible with low temperature tar and-that the solution is a uniform and stable fluid under the usual conditions of handling and use. However, the characteristics of low temperature tars difier in degree from each other, as do also those of high temperature tar-pitches. Therefore, the relative quantities of the two required to produce a mixture of given fluidity-for instance, that essential to use in the spraying equipment of a steel mill also varies but the relative quantities of any particular tar and pitch required can readily be determined empirically by the skilled artisan who makes the mixture, the addition of more low temperature tar increasing and the addition of more pitch decreasing the fluidity. By way of illustrative example, in a test ovens.

He has it in his hands, therefore, to produce as much low temperature tar as he needs. The serious objection as to uncertain or unsteady supply is overcome.

The low temperature tar may be used as it is produced. However, I prefer to remove its lighter constituents, or with other words, top it, before using it as a solvent for the coke oven pitch. This topped low temperature tar has the advantage that it burns more steadily 'insolution with the pitch.

A portion of the low boiling cresote oils in many coke oven tars, is of such light specific gravity, that it does not meet the best requirements of wood'preserving oils. This low boiling portion may be added to the solution of oven tar pitch in low temperature tar to good advantage.

I claim:

1. As a liquid fuel for metallurgical furnaces a; hydrocarbon liquid consisting of the pitch residuum of high temperature cokeoven tar from which so much creosote oil has been removed as to render the residuum. non-fluid at normal temperature, dissolved in and held in stable solution by low temperature coal tar, the low temperature coal tar being of such proportion in the liquid relative to the pitch residuum therein that the mixture when moderately preheated is thereby maintained a permanent solution fluid at normal temperature.

2'. As a fuel,.a hydrocarbonliquid consisting of the residuumof,high'temperature coke oven tar from which so much wood preserv- 1' ing oil has been removed as to render the residuum non-fluid at normal temperature,

dissolved and held in stable solution by'low temperature'tar, the low temperature'tar being of such proportion in the liquid relative r to the said residuum of high-temperature coke oven tar therein that the mixture when moderately preheated is thereby maintained a permanent solution fluid at normal temperature.

FRANZ PUENING.

made by me, taking residual pitch left over after removing oil equal to about 45% from Youngstown tar made from Pittsburgh coal in Koppers ovens and slowly adding to .5 liter of such molten pitch topped low temperature tar made from southern Illinois coal and thoroughly mixing, I found that .9 liter of the latter produced a mixture whose fluidity was about that of the average coke oven 

